Wound dressing and method of use

ABSTRACT

A system, method, and apparatus are disclosed for dressing a wound. The apparatus comprises a liquid and gas permeable transmission layer, an absorbent layer for absorbing wound exudate, the absorbent layer overlying the transmission layer, a gas impermeable cover layer overlying the absorbent layer and comprising a first orifice, wherein the cover layer is moisture vapor permeable.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/633,670, filed on Jun. 26, 2017, which is a continuation of U.S.patent application Ser. No. 14/715,399, filed on May 18, 2015 and issuedas U.S. Pat. No. 9,808,561, which is a continuation of U.S. patentapplication Ser. No. 13/092,042, filed on Apr. 21, 2011 and issued asU.S. Pat. No. 9,061,095, which claims priority to Great Britain PatentApplication No. 1006986.2, filed Apr. 27, 2010; Great Britain PatentApplication No. 1006983.9, filed Apr. 27, 2010; Great Britain PatentApplication No. 1006985.4, filed Apr. 27, 2010; Great Britain PatentApplication No. 1006988.8, filed Apr. 27, 2010; and Great Britain PatentApplication No. 1008347.5, filed May 19, 2010; all of which are herebyincorporated by reference in their entirety.

BACKGROUND OF THE INVENTION Field of the Invention

Embodiments of the present invention relate to methods and apparatusesfor dressing and treating a wound with topical negative pressure (TNP)therapy. In particular, but not exclusively, embodiments disclosedherein relate to a wound dressing for providing protection to a woundsite, in which the wound dressing acts as a buffer to help preventcompression or shear forces exerted on the wound dressing, for exampledue to patient movement, from harming a healing wound. Embodiments ofthe wound dressing may act as a waste canister to collect and storewound exudate removed from a wound site, and also relate to themanagement of solid build-up in a wound dressing covering a wound sitewhilst TNP therapy is applied. Further, embodiments disclosed hereinrelate to a method and suction port for applying negative pressure to awound dressing and a method of manufacturing a suction port and wounddressing.

Description of the Related Art

Many different types of wound dressing are known for aiding in thehealing process of a human or animal. These different types of wounddressing include many different types of materials and layers, forexample, gauze, pads, foam pads or multi-layer wound dressings.

In addition, TNP therapy, sometimes referred as vacuum assisted closureor negative pressure wound therapy, has recently been proposed as asuccessful mechanism for improving the healing rate of a wound. Suchtherapy is applicable to a broad range of wounds such as incisionalwounds, open wounds and abdominal wounds or the like.

TNP therapy assists in the closure and healing of wounds by reducingtissue oedema; encouraging blood flow; stimulating the formation ofgranulation tissue; removing excess exudates and may reduce bacterialload and thus, infection to the wound. Furthermore, TNP therapy permitsless outside disturbance of the wound and promotes more rapid healing.

During TNP therapy, a suction source such as a vacuum pump or the likeis utilized to create a negative pressure region. That is to say, aregion where an experienced pressure is below that of the surroundings.Wound exudate and other potentially harmful material is extracted fromthe wound region and must be stored for later disposal. A problemassociated with many known techniques is that a separate canister mustbe provided for storage of such exudate. Provision of such canisters iscostly and bulky and prone to failure.

A proposal has been suggested to store extracted wound exudate in thewound dressing itself that is used to cover a wound site and create thewound chamber region where negative pressure is established. However, itis known that many different wound types can exude high flow rates ofexudate and therefore storage of exuding material in a wound dressingcan be problematical since the wound dressing will only have a limitedcapacity for fluid uptake before a dressing change is required. This canlimit a time of use between dressing changes and can prove costly ifmany wound dressings are required to treat a given wound.

It has been suggested as a solution to this problem, that a liquidimpermeable moisture vapor permeable cover layer can be utilized as anuppermost cover layer for the wound dressing. The air impermeable natureof the cover layer provides a sealing layer over the wound site so thatnegative pressure can be established below the dressing in the region ofthe wound. The moisture vapor permeability of this covering layer isselected so that liquid can constantly evaporate away from the top ofthe dressing. This means that as therapy is continued the dressing doesnot have to take up and hold all liquid exuding from the wound. Rather,some liquid is constantly escaping in the form of moisture vapor fromthe upper environs of the dressing.

Whilst such dressings work well in practice, the continuous evaporationof moisture vapor from the dressing can lead to the problem of crustformation in the dressing. That is to say, because of the continuousdrawing of liquid away from the wound site solid particulate matter ismore prone to formation and accumulation in the dressing. Under certaincircumstances the build-up of such solid material can lead to blockagesforming in the wound dressing in the flowpath between the wound and thesource of negative pressure. This can potentially cause problems in thattherapy may need to be halted to change a dressing if the blockagesreach a critical level.

Further, there is much prior art available relating to the provision ofapparatuses and methods of use thereof for the application of TNPtherapy to wounds together with other therapeutic processes intended toenhance the effects of the TNP therapy.

It will be appreciated that from time to time accidents may happen topatients undergoing negative pressure wound therapy. Such accidentsmight cause short term or long term forces to be applied to a dressingcovering a wound. Alternatively patient movement may bring the patientand any dressing covering a healing wound into contact with an externalobject. In such occurrences compressive forces or lateral forces mayoccur. Such force can cause disturbance of a wound bed which can damagea wound site. A particular cause for concern is during the treatment ofskin graft wounds. Under such conditions lateral forces can entirelyupset or tear apart a healing skin graft region.

SUMMARY OF THE INVENTION

It is an aim of certain embodiments of the present invention to at leastpartly mitigate the above-mentioned problems.

It is an aim of certain embodiments of the present invention to providea method for providing negative pressure at a wound site to aid in woundclosure and healing in which wound exudate drawn from a wound siteduring the therapy is collected and stored in a wound dressing.

It is an aim of certain embodiments of the present invention to providea wound dressing having an increased capacity for absorbing woundexudate reducing the frequency with which the dressings must be changed.

It is further an aim of certain embodiments of the invention to managethe movement of wound exudate through a dressing to avoid blockagesoccurring that lead to reduced life of the dressing.

It is an aim of certain embodiments of the present invention to providea wound dressing having an increased capacity to absorb compressiveforces exerted on the wound dressing.

It is an aim of certain embodiments of the present invention to providea wound dressing having an increased capacity to prevent shear forcesfrom an outer surface of a wound dressing from being translated intocorresponding shear forces at a wound site.

It is an aim of certain embodiments of the present invention to providea wound dressing which can “give” in a direction perpendicular to andparallel to a wound site surface even when the dressing experiencesnegative pressure.

It is an aim of certain embodiments of the present invention to providea wound dressing able to be used with topical negative pressure therapywhich helps maintain an open flow path so that therapy can be continuedunhindered by blockages caused by build-up of solid matter.

It is an aim of certain embodiments of the present invention to providea method and apparatus for treating a wound with topical negativepressure therapy by preventing blockage of a flowpath region of a wounddressing.

Embodiments disclosed herein are directed toward the treatment of woundswith TNP. In particular, certain embodiments disclose a wound dressingcapable of absorbing and storing wound exudate in conjunction with apump, for example a miniaturized pump. Some wound dressing embodimentsfurther comprise a transmission layer configured to transmit woundexudates to an absorbent layer disposed in the wound dressing.Additionally, some embodiments provide for a port or other fluidicconnector configured to retain wound exudate within the wound dressingwhile transmitting negative pressure to the wound dressing.

According to a first embodiment of the present invention there isprovided a wound treatment apparatus comprising: a wound dressingcomprising:

-   -   a transmission layer comprising a 3D knitted or fabric material        configured to remain open upon application of negative pressure        to the wound dressing;    -   an absorbent layer for absorbing wound exudate, the absorbent        layer overlying the transmission layer;    -   a cover layer overlying the absorbent layer and comprising an        orifice, wherein the cover layer is moisture vapor permeable;    -   a pump; and    -   a suction port for applying negative pressure to the wound        dressing for the application of topical negative pressure at a        wound site, the suction port comprising:    -   a connector portion for connecting the suction port to the pump;    -   a sealing surface for sealing the suction port to the cover        layer of the wound dressing; and    -   a liquid impermeable gas permeable filter element arranged to        prevent a liquid from entering the connector portion.

According to a second embodiment of the present invention there isprovided a method for the treatment of a wound comprising:

-   -   providing a wound dressing comprising:        -   a transmission layer comprising a 3D knitted or fabric            material;        -   an absorbent layer for absorbing wound exudate, the            absorbent layer overlying the transmission layer;        -   a cover layer overlying the absorbent layer and comprising            an orifice, wherein the cover layer is moisture vapor            permeable;    -   positioning the dressing over a wound site to form a sealed        cavity over the wound site; and    -   applying negative pressure to the wound site to draw fluid        through the transmission layer into the absorbent layer.

According to a another embodiment of the present invention there isprovided a wound dressing for providing protection at a wound site,comprising:

-   -   a transmission layer comprising a first surface and a further        surface spaced apart from the first surface by a relax distance        in a relaxed mode of operation; and    -   a plurality of spacer elements extending between the first and        further surfaces and, in a forced mode of operation, locatable        whereby the first and further surfaces are spaced apart by a        compression distance less than the relax distance.

According to a one embodiment of the present invention there is provideda method for providing protection at a wound site, comprising:

-   -   locating a wound dressing comprising a transmission layer over a        wound site;

and

-   -   responsive to a force on the wound dressing, displacing a        plurality of spacer elements extending between a first surface        and a further surface of the transmission layer whereby;    -   a distance between the first and further surfaces is reduced as        the spacer elements are displaced.

According to another embodiment of the present invention there isprovided an apparatus for dressing a wound for the application oftopical negative pressure at a wound site, comprising:

-   -   a liquid and gas permeable transmission layer;    -   an absorbent layer for absorbing wound exudate, the absorbent        layer overlying the transmission layer;    -   a gas impermeable cover layer overlying the absorbent layer and        comprising a first orifice, wherein the cover layer is moisture        vapor permeable.

According to a further embodiment of the present invention there isprovided a method of applying TNP at a wound site, comprising the stepsof:

-   -   applying negative pressure at an orifice of a cover layer of a        wound dressing, a peripheral region around the wound site being        sealed with the wound dressing, such that air and wound exudate        are drawn towards the orifice;    -   collecting wound exudate, drawn from the wound site, through a        transmission layer of the wound dressing, in an absorbent layer        of the wound dressing; and    -   transpiring a water component of the wound exudate collected in        the absorbent layer through the cover layer of the wound        dressing.

According to an additional embodiment of the present invention there isprovided apparatus for dressing a wound for the application of topicalnegative pressure at a wound site, comprising:

-   -   a liquid and gas permeable transmission layer;    -   an absorbent layer for absorbing wound exudate;    -   a gas impermeable cover layer overlying the absorbent layer and        the transmission layer, the cover layer comprising an orifice        connected to the transmission layer; and    -   at least one element configured to reduce the rate at which        wound exudate moves towards the orifice when a negative pressure        is applied at the orifice.

According to another embodiment of the present invention there isprovided a method of applying TNP at a wound site, comprising the stepsof:

-   -   applying negative pressure at an orifice of a cover layer of a        wound dressing, a peripheral region around the wound site being        sealed with the wound dressing such that air and wound exudate        move towards the orifice;    -   collecting wound exudate, from the wound site, through a        transmission layer of the wound dressing, in an absorbent layer        of the wound dressing; and    -   reducing the rate at which wound exudate moves towards the        orifice.

According to still another embodiment of the present invention there isprovided apparatus for dressing a wound for the application of topicalnegative pressure at a wound site, comprising:

-   -   an absorbent layer for absorbing wound exudate;    -   a gas impermeable cover layer overlying the absorbent layer the        cover layer comprising at least one orifice configured to allow        negative pressure to be communicated through the cover layer in        at least two spaced apart regions.

According to an additional embodiment of the present invention there isprovided a method of applying TNP at a wound site, comprising the stepsof:

-   -   sealing a cover layer of a wound dressing around the wound site;    -   applying negative pressure at at least one orifice in the cover        layer, said at least one orifice configured to allow negative        pressure to be communicated through the cover layer in at least        two spaced apart regions; and    -   collecting wound exudate, from the wound site, in an absorbent        layer of the wound dressing.

According to one embodiment of the present invention there is provided asuction port for applying negative pressure to a wound dressing for theapplication of topical negative pressure at a wound site, the suctionport comprising:

-   -   a connector portion for connecting the suction port to a source        of negative pressure;    -   a sealing surface for sealing the suction port to a cover layer        of a wound dressing; and    -   a liquid impermeable gas permeable filter element arranged to        prevent a liquid entering the connector portion.

According to an additional embodiment of the present invention there isprovided a method of communicating negative pressure to a wound dressingfor the application of topical negative pressure at a wound site,comprising the steps of:

-   -   applying negative pressure at a connecting portion of a suction        port sealed around a perimeter of an orifice in a cover layer of        the wound dressing;    -   filtering gas drawn from within the wound dressing through a        liquid impermeable gas permeable filter element of the suction        port.

According to another embodiment of the invention there is provided amethod of manufacturing a suction port for applying negative pressure toa wound dressing for the application of topical negative pressure at awound site, the suction port having a connector portion for connectingthe suction port to a source of negative pressure and a sealing surfacefor sealing the suction port to a cover layer of a wound dressing, themethod comprising:

-   -   disposing a liquid impermeable gas permeable filter element of        the suction port at a location to prevent a liquid entering the        connector portion.

According to yet another embodiment of the present invention there isprovided apparatus for the application of TNP therapy to a wound site,comprising:

-   -   a first layer comprising a plurality of openings each having a        first open area;    -   a further layer spaced apart from the first layer comprising a        plurality of further openings each having a further open area;        and    -   an air impermeable, moisture vapor permeable cover layer over        the first and further layers; wherein    -   a region between the first and further layers comprises a        portion of a flow path for air and/or wound exudate flowing from        a wound site and said first open area is less than said further        open area.

According to still another embodiment of the present invention there isprovided a method of applying TNP therapy to a wound site, comprising:

-   -   via a vacuum pump in fluid communication with a wound dressing        located over a wound site, applying a negative pressure at the        wound site; and    -   as liquid evaporates through a cover layer of the dressing,        preventing blockage of a fluid flowpath region of the wound        dressing.

Certain embodiments provide a wound dressing which even when undernegative pressure conditions is able to provide further “give” to buffercompression forces from harming a wound.

Certain embodiments provide a wound dressing able to disconnect shearforces applied to the dressing from the wound site covered by thedressing. As a result damage to the wound can be wholly or at leastpartially avoided.

Certain embodiments provide the advantage that a wound site can becovered with a wound dressing which is simultaneously able to delivernegative pressure wound therapy to a wound site, collect exudate andprovide protection from forces operating on the dressing.

Certain embodiments provide the advantage that forces operating on adressing can be offset by dissipating loads operating over a relativelysmall distance on an upper layer of the dressing to a relatively largerarea on a lower surface of the dressing. The force is thus dissipatedover a larger area thus reducing the effect of the force.

Certain embodiments provide the advantage that a wound dressing can beused to collect wound exudate generated during a negative pressuretherapy process, whilst extending the useful lifetime of the dressing bytranspiring a water component of the wound exudate. A pump remote fromthe wound dressing can be connected to the wound dressing and reusedwhilst the wound dressing itself is used to collect wound exudate andmay then be disposed of after use.

Certain embodiments provide a wound dressing and/or method of applyingtopical negative pressure in which a flowpath through a wound dressingis kept open so that therapy can be continued for as long as desired bya care giver.

Certain embodiments prevent solid material, which may cause a blockage,from entering a flowpath region in the wound dressing by using a layerof the dressing to act as a bar to such material.

Certain embodiments prevent build-up of solid material in a flowpathregion of a wound dressing by ensuring that any solid material thatenters into that flowpath region can always escape into a further regionof the dressing.

Certain embodiments provide the advantage that the build-up of solidmaterial in a flowpath in a wound dressing is avoided by having anabsorbent layer close to the flowpath region store liquid over time.This helps keep the environment of the flowpath region moist which helpsavoid crusting.

Certain embodiments provide the advantage that a wound dressing can beused to collect wound exudate generated during a negative pressuretherapy process, whilst extending the useful lifetime of the dressing bytranspiring a water component of the wound exudate. A pump remote fromthe wound dressing can be connected to the wound dressing and reusedwhilst the wound dressing itself is used to collect wound exudate andmay then be disposed of after use.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described hereinafter,by way of example only, with reference to the accompanying drawings inwhich:

FIG. 1A illustrates a wound dressing;

FIG. 1B illustrates another embodiment of a wound dressing;

FIG. 2 illustrates a top view of a wound dressing;

FIG. 3 illustrates a top view of a wound dressing including baffleelements;

FIG. 4 illustrates a top view of a further wound dressing includingbaffle elements;

FIG. 5 illustrates a baffle element according to one embodiment;

FIG. 6 illustrates a top view of a wound dressing including a singlebaffle element;

FIG. 7 illustrates a top view of a wound dressing including an airchannel;

FIG. 8 illustrates a top view of a wound dressing including two airchannels;

FIG. 9 illustrates a top view of a wound dressing including two orificesin a cover layer coupled through a fluid communication passage;

FIG. 10 illustrates an embodiment of the fluid communication passage;

FIG. 11 illustrates a top view of a suction port;

FIG. 12 illustrates a suction port including a filter element;

FIG. 13 illustrates a further suction port including a filter element;

FIGS. 14A-L illustrate a range of exemplifying configurations of baffleelements in a wound dressing;

FIG. 15 illustrates an exemplifying configuration of vias in atransmission layer of a wound dressing;

FIG. 16 illustrates a top view of a wound dressing including an elongateorifice in a cover layer;

FIG. 17 illustrates a transmission layer in a relaxed mode of operation;

FIG. 18 illustrates a transmission layer in a forced mode of operation;

FIG. 19 illustrates pressure offsetting;

FIG. 20 illustrates a transmission layer and overlying absorbent layerin a relaxed mode of operation;

FIG. 21 illustrates an absorbent layer and transmission layerexperiencing a compressive force;

FIG. 22 illustrates an absorbent layer and transmission layerexperiencing a shear force;

FIG. 23 illustrates a cross-section of a region of an embodiment of awound dressing;

FIG. 24 illustrates a lower layer of a transmission layer used in anembodiment of a wound dressing;

FIG. 25 illustrates an upper layer of a transmission layer used in anembodiment of a wound dressing;

FIG. 26 illustrates a lower surface of a transmission layer used inanother embodiment of a wound dressing;

FIG. 27 illustrates an upper surface of a transmission layer used inanother embodiment of a wound dressing;

FIG. 28 illustrates an embodiment of a wound treatment system; and,

FIGS. 29A-D illustrate the use and application of an embodiment of awound treatment system onto a patient.

In the drawings like reference numerals refer to like parts.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1A-B illustrate cross sections through a wound dressing 100according to an embodiment of the invention. A plan view from above thewound dressing 100 is illustrated in FIG. 2 with the line A-A indicatingthe location of the cross section shown in FIGS. 1A and 1B. It will beunderstood that FIGS. 1A-B illustrate a generalized schematic view of anapparatus 100. It will be understood that embodiments of the presentinvention are generally applicable to use in TNP therapy systems.Briefly, negative pressure wound therapy assists in the closure andhealing of many forms of “hard to heal” wounds by reducing tissueoedema; encouraging blood flow and granular tissue formation; removingexcess exudate and may reduce bacterial load (and thus infection risk).In addition, the therapy allows for less disturbance of a wound leadingto more rapid healing. TNP therapy systems may also assist on thehealing of surgically closed wounds by removing fluid and by helping tostabilize the tissue in the apposed position of closure. A furtherbeneficial use of TNP therapy can be found in grafts and flaps whereremoval of excess fluid is important and close proximity of the graft totissue is required in order to ensure tissue viability.

The wound dressing 100 can be located over a wound site to be treated.The dressing 100 forms a sealed cavity over the wound site. It will beappreciated that throughout this specification reference is made to awound. In this sense it is to be understood that the term wound is to bebroadly construed and encompasses open and closed wounds in which skinis torn, cut or punctured or where trauma causes a contusion. A wound isthus broadly defined as any damaged region of tissue where fluid may ormay not be produced. Examples of such wounds include, but are notlimited to, incisions, lacerations, abrasions, contusions, burns,diabetic ulcers, pressure ulcers, stoma, surgical wounds, trauma andvenous ulcers or the like.

In some embodiments, it may be preferable for the wound site to befilled partially or completely with a wound packing material. This woundpacking material is optional, but may be desirable in certain wounds,for example deeper wounds. The wound packing material can be used inaddition to the wound dressing 100. The wound packing material generallymay comprise a porous and conformable material, for example foam(including reticulated foams), and gauze. Preferably, the wound packingmaterial is sized or shaped to fit within the wound site so as to fillany empty spaces. The wound dressing 100 may then be placed over thewound site and wound packing material overlying the wound site. When awound packing material is used, once the wound dressing 100 is sealedover the wound site, TNP is transmitted from a pump through the wounddressing 100, through the wound packing material, and to the wound site.This negative pressure draws wound exudate and other fluids orsecretions away from the wound site.

It is envisaged that the negative pressure range for the apparatusembodying the present invention may be between about −20 mmHg and −200mmHg (note that these pressures are relative to normal ambientatmospheric pressure thus, −200 mmHg would be about 560 mmHg inpractical terms). In one embodiment, the pressure range may be betweenabout −40 mmHg and −150 mmHg. Alternatively a pressure range of up to−75 mmHg, up to −80 mmHg or over −80 mmHg can be used. Also in otherembodiments a pressure range of below −75 mmHg could be used.Alternatively a pressure range of over −100 mmHg could be used or over−150 mmHg.

It will be appreciated that according to certain embodiments of thepresent invention the pressure provided may be modulated over a periodof time according to one or more desired and predefined pressureprofiles. For example such a profile may include modulating the negativepressure between two predetermined negative pressures P1 and P2 suchthat pressure is held substantially constant at P1 for a pre-determinedtime period T1 and then adjusted by suitable means such as varying pumpwork or restricting fluid flow or the like, to a new predeterminedpressure P2 where the pressure may be held substantially constant for afurther predetermined time period T2. Two, three or four or morepredetermined pressure values and respective time periods may beoptionally utilized. Other embodiments may employ more complexamplitude/frequency wave forms of pressure flow profiles may also beprovided e.g. sinusoidal, sore tooth, systolic-diastolic or the like.

As illustrated in FIGS. 1A-B a lower surface 101 of the wound dressing100 is provided by an optional wound contact layer 102. The woundcontact layer 102 can be a polyurethane layer or polyethylene layer orother flexible layer which is perforated, for example via a hot pinprocess, laser ablation process, ultrasound process or in some other wayor otherwise made permeable to liquid and gas. The wound contact layerhas a lower surface 101 and an upper surface 103. The perforations 104are through holes in the wound contact layer which enables fluid to flowthrough the layer. The wound contact layer helps prevent tissue ingrowthinto the other material of the wound dressing. The perforations aresmall enough to meet this requirement but still allow fluid through. Forexample, perforations formed as slits or holes having a size rangingfrom 0.025 mm to 1.2 mm are considered small enough to help preventtissue ingrowth into the wound dressing while allowing wound exudate toflow into the dressing. The wound contact layer helps hold the wholewound dressing together and helps to create an air tight seal around theabsorbent pad in order to maintain negative pressure at the wound. Thewound contact layer also acts as a carrier for an optional lower andupper adhesive layer (not shown). For example, a lower pressuresensitive adhesive may be provided on the underside surface 101 of thewound dressing whilst an upper pressure sensitive adhesive layer may beprovided on the upper surface 103 of the wound contact layer. Thepressure sensitive adhesive, which may be a silicone, hot melt,hydrocolloid or acrylic based adhesive or other such adhesives, may beformed on both sides or optionally on a selected one or none of thesides of the wound contact layer. When a lower pressure sensitiveadhesive layer is utilized this helps adhere the wound dressing to theskin around a wound site.

A layer 105 of porous material is located above the wound contact layer.This porous layer, or transmission layer, 105 allows transmission offluid including liquid and gas away from a wound site into upper layersof the wound dressing. In particular, the transmission layer 105 ensuresthat an open air channel can be maintained to communicate negativepressure over the wound area even when the absorbent layer has absorbedsubstantial amounts of exudates. The layer should remain open under thetypical pressures that will be applied during negative pressure woundtherapy as described above, so that the whole wound site sees anequalized negative pressure. The layer 105 is formed of a materialhaving a three dimensional structure. For example, a knitted or wovenspacer fabric (for example Baltex 7970 weft knitted polyester) or anon-woven fabric could be used. Other materials could of course beutilized, and examples of such materials are described below withrespect to FIGS. 23-27.

In some embodiments, the transmission layer comprises a 3D polyesterspacer fabric layer including a top layer (that is to say, a layerdistal from the wound-bed in use) which is a 84/144 textured polyester,and a bottom layer (that is to say, a layer which lies proximate to thewound bed in use) which is a 100 denier flat polyester and a third layerformed sandwiched between these two layers which is a region defined bya knitted polyester viscose, cellulose or the like monofilament fiber.Other materials and other linear mass densities of fiber could of coursebe used.

Whilst reference is made throughout this disclosure to a monofilamentfiber it will be appreciated that a multistrand alternative could ofcourse be utilized.

The top spacer fabric thus has more filaments in a yarn used to form itthan the number of filaments making up the yarn used to form the bottomspacer fabric layer.

This differential between filament counts in the spaced apart layershelps control moisture flow across the transmission layer. Particularly,by having a filament count greater in the top layer, that is to say, thetop layer is made from a yarn having more filaments than the yarn usedin the bottom layer, liquid tends to be wicked along the top layer morethan the bottom layer. In use, this differential tends to draw liquidaway from the wound bed and into a central region of the dressing wherethe absorbent layer helps lock the liquid away or itself wicks theliquid onwards towards the cover layer where it can be transpired.

Preferably, to improve the liquid flow across the transmission layer(that is to say perpendicular to the channel region formed between thetop and bottom spacer layers, the 3D fabric is treated with a drycleaning agent (such as, but not limited to, Perchloro Ethylene) to helpremove any manufacturing products such as mineral oils, fats and/orwaxes used previously which might interfere with the hydrophiliccapabilities of the transmission layer. In some embodiments, anadditional manufacturing step can subsequently be carried in which the3D spacer fabric is washed in a hydrophilic agent (such as, but notlimited to, Feran Ice 30 g/l available from the Rudolph Group). Thisprocess step helps ensure that the surface tension on the materials isso low that liquid such as water can enter the fabric as soon as itcontacts the 3D knit fabric. This also aids in controlling the flow ofthe liquid insult component of any exudates.

A layer 110 of absorbent material is provided above the transmissionlayer 105. The absorbent material which may be a foam or non-wovennatural or synthetic material and which may optionally include or besuper-absorbent material forms a reservoir for fluid, particularlyliquid, removed from the wound site and draws those fluids towards acover layer 140. The material of the absorbent layer also preventsliquid collected in the wound dressing from flowing in a sloshingmanner. The absorbent layer 110 also helps distribute fluid throughoutthe layer via a wicking action so that fluid is drawn from the woundsite and stored throughout the absorbent layer. This helps preventagglomeration in areas of the absorbent layer. The capacity of theabsorbent material must be sufficient to manage the exudates flow rateof a wound when negative pressure is applied. Since in use the absorbentlayer experiences negative pressures the material of the absorbent layeris chosen to absorb liquid under such circumstances. A number ofmaterials exist that are able to absorb liquid when under negativepressure, for example superabsorber material. The absorbent layer 110may typically be manufactured from ALLEVYN™ foam, Freudenberg 114-224-4and/or Chem-Posite™ 11C-450.

In some embodiments, the absorbent layer is a layer of non-wovencellulose fibers having super-absorbent material in the form of dryparticles dispersed throughout. Use of the cellulose fibers introducesfast wicking elements which help quickly and evenly distribute liquidtaken up by the dressing. The juxtaposition of multiple strand-likefibers leads to strong capillary action in the fibrous pad which helpsdistribute liquid. In this way, the super-absorbent material isefficiently supplied with liquid. Also, all regions of the absorbentlayer are provided with liquid.

The wicking action also assists in bringing liquid into contact with theupper cover layer to aid increase transpiration rates of the dressing.

The wicking action also assists in delivering liquid downwards towardsthe wound bed when exudation slows or halts. This delivery process helpsmaintain the transmission layer and lower wound bed region in a moiststate which helps prevent crusting within the dressing (which could leadto blockage) and helps maintain an environment optimized for woundhealing.

In some embodiments, the absorbent layer may be an air-laid material.Heat fusible fibers may optionally be used to assist in holding thestructure of the pad together. It will be appreciated that rather thanusing super-absorbing particles or in addition to such use,super-absorbing fibers may be utilized according to certain embodimentsof the present invention. An example of a suitable material is theProduct Chem-Posite™ 11 C available from Emerging Technologies Inc (ETi)in the USA.

Optionally, according to certain embodiments of the present invention,the absorbent layer may include synthetic stable fibers and/orbi-component stable fibers and/or natural stable fibers and/orsuper-absorbent fibers. Fibers in the absorbent layer may be securedtogether by latex bonding or thermal bonding or hydrogen bonding or acombination of any bonding technique or other securing mechanism. Insome embodiments, the absorbent layer is formed by fibers which operateto lock super-absorbent particles within the absorbent layer. This helpsensure that super-absorbent particles do not move external to theabsorbent layer and towards an underlying wound bed. This isparticularly helpful because when negative pressure is applied there isa tendency for the absorbent pad to collapse downwards and this actionwould push super-absorbent particle matter into a direction towards thewound bed if they were not locked away by the fibrous structure of theabsorbent layer.

The absorbent layer may comprise a layer of multiple fibers. Preferably,the fibers are strand-like and made from cellulose, polyester, viscoseor the like. Preferably, dry absorbent particles are distributedthroughout the absorbent layer ready for use. In some embodiments, theabsorbent layer comprises a pad of cellulose fibers and a plurality ofsuper absorbent particles. In additional embodiments, the absorbentlayer is a non-woven layer of randomly orientated cellulose fibers.

Super-absorber particles/fibers may be, for example, sodium polyacrylateor carbomethoxycellulose materials or the like or any material capableof absorbing many times its own weight in liquid. In some embodiments,the material can absorb more than five times its own weight of 0.9% W/Wsaline, etc. In some embodiments, the material can absorb more than 15times its own weight of 0.9% W/W saline, etc. In some embodiments, thematerial is capable of absorbing more than 20 times its own weight of0.9% W/W saline, etc. Preferably, the material is capable of absorbingmore than 30 times its own weight of 0.9% W/W saline, etc.

Preferably, the particles of superabsorber are very hydrophilic and grabthe fluid as it enters the dressing, swelling up on contact. Anequilibrium is set up within the dressing core whereby moisture passesfrom the superabsorber into the dryer surrounding area and as it hitsthe top film the film switches and the fluid vapor starts to betranspired. A moisture gradient is established within the dressing tocontinually remove fluid from the wound bed and ensure the dressing doesnot become heavy with exudate.

Preferably the absorbent layer includes at least one through holelocated so as to underly the suction port. As illustrated in FIGS. 1A-Ba single through hole can be used to produce an opening underlying theport 150. It will be appreciated that multiple openings couldalternatively be utilized. Additionally should more than one port beutilized according to certain embodiments of the present invention oneor multiple openings may be made in the super-absorbent layer inregistration with each respective port. Although not essential tocertain embodiments of the present invention the use of through holes inthe super-absorbent layer provide a fluid flow pathway which isparticularly unhindered and this is useful in certain circumstances.

Where an opening is provided in the absorbent layer the thickness of thelayer itself will act as a stand-off separating any overlying layer fromthe upper surface (that is to say the surface facing away from a woundin use) of the transmission layer 105. An advantage of this is that thefilter of the port is thus decoupled from the material of thetransmission layer. This helps reduce the likelihood that the filterwill be wetted out and thus will occlude and block further operation.

Use of one or more through holes in the absorption layer also has theadvantage that during use if the absorbent layer contains a gel formingmaterial, such as superabsorber, that material as it expands to absorbliquid, does not form a barrier through which further liquid movementand fluid movement in general cannot pass. In this way each opening inthe absorbent layer provides a fluid pathway between the transmissionlayer directly to the wound facing surface of the filter and thenonwards into the interior of the port.

A gas impermeable, but moisture vapor permeable, cover layer 140 extendsacross the width of the wound dressing. The cover layer, which may forexample be a polyurethane film (for example, Elastollan SP9109) having apressure sensitive adhesive on one side, is impermeable to gas and thislayer thus operates to cover the wound and to seal a wound cavity overwhich the wound dressing is placed. In this way an effective chamber ismade between the cover layer and a wound site where a negative pressurecan be established. The cover layer 140 is sealed to the wound contactlayer 102 in a border region 200 around the circumference of thedressing, ensuring that no air is drawn in through the border area, forexample via adhesive or welding techniques. The cover layer 140 protectsthe wound from external bacterial contamination (bacterial barrier) andallows liquid from wound exudates to be transferred through the layerand evaporated from the film outer surface. The cover layer 140typically comprises two layers; a polyurethane film and an adhesivepattern spread onto the film. The polyurethane film is moisture vaporpermeable and may be manufactured from a material that has an increasedwater transmission rate when wet.

The absorbent layer 110 may be of a greater area than the transmissionlayer 105, such that the absorbent layer overlaps the edges of thetransmission layer 105, thereby ensuring that the transmission layerdoes not contact the cover layer 140. This provides an outer channel 115of the absorbent layer 110 that is in direct contact with the woundcontact layer 102, which aids more rapid absorption of exudates to theabsorbent layer. Furthermore, this outer channel 115 ensures that noliquid is able to pool around the circumference of the wound cavity,which may otherwise seep through the seal around the perimeter of thedressing leading to the formation of leaks.

In order to ensure that the air channel remains open when a vacuum isapplied to the wound cavity, the transmission layer 105 must besufficiently strong and non-compliant to resist the force due to thepressure differential. However, if this layer comes into contact withthe relatively delicate cover layer 140, it can cause the formation ofpin-hole openings in the cover layer 140 which allow air to leak intothe wound cavity. This may be a particular problem when a switchabletype polyurethane film is used that becomes weaker when wet. Theabsorbent layer 110 is generally formed of a relatively soft,non-abrasive material compared to the material of the transmission layer105 and therefore does not cause the formation of pin-hole openings inthe cover layer. Thus by providing an absorbent layer 110 that is ofgreater area than the transmission layer 105 and that overlaps the edgesof the transmission layer 105, contact between the transmission layerand the cover layer is prevented, avoiding the formation of pin-holeopenings in the cover layer 140.

The absorbent layer 110 is positioned in fluid contact with the coverlayer 140. As the absorbent layer absorbs wound exudate, the exudate isdrawn towards the cover layer 140, bringing the water component of theexudate into contact with the moisture vapor permeable cover layer. Thiswater component is drawn into the cover layer itself and then evaporatesfrom the top surface of the dressing. In this way, the water content ofthe wound exudate can be transpired from the dressing, reducing thevolume of the remaining wound exudate that is to be absorbed by theabsorbent layer 110, and increasing the time before the dressing becomesfull and must be changed. This process of transpiration occurs even whennegative pressure has been applied to the wound cavity, and it has beenfound that the pressure difference across the cover layer when anegative pressure is applied to the wound cavity has negligible impacton the moisture vapor transmission rate across the cover layer.

An orifice 145 is provided in the cover film 140 to allow a negativepressure to be applied to the dressing 100. A suction port 150 is sealedto the top of the cover film 140 over the orifice 145, and communicatesnegative pressure through the orifice 145. A length of tubing 220 may becoupled at a first end to the suction port 150 and at a second end to apump unit (not shown) to allow fluids to be pumped out of the dressing.The port may be adhered and sealed to the cover film 140 using anadhesive such as an acrylic, cyanoacrylate, epoxy, UV curable or hotmelt adhesive. The port 150 is formed from a soft polymer, for example apolyethylene, a polyvinyl chloride, a silicone or polyurethane having ahardness of 30 to 90 on the Shore A scale.

An aperture or through-hole 146 is provided in the absorbent layer 110beneath the orifice 145 such that the orifice is connected directly tothe transmission layer 105. This allows the negative pressure applied tothe port 150 to be communicated to the transmission layer 105 withoutpassing through the absorbent layer 110. This ensures that the negativepressure applied to the wound site is not inhibited by the absorbentlayer as it absorbs wound exudates. In other embodiments, no aperturemay be provided in the absorbent layer 110, or alternatively a pluralityof apertures underlying the orifice 145 may be provided.

As shown in FIG. 1A, one embodiment of the wound dressing 100 comprisesan aperture 146 in the absorbent layer 100 situated underneath the port150. In use, for example when negative pressure is applied to thedressing 100, a wound facing portion of the port 150 may thus come intocontact with the transmission layer 105, which can thus aid intransmitting negative pressure to the wound site even when the absorbentlayer 110 is filled with wound fluids. Some embodiments may have thecover layer 140 be at least partly adhered to the transmission layer105. In some embodiments, the aperture 146 is at least 1-2 mm largerthan the diameter of the wound facing portion of the port 150, or theorifice 145.

A filter element 130 that is impermeable to liquids, but permeable togases is provided to act as a liquid barrier, and to ensure that noliquids are able to escape from the wound dressing. The filter elementmay also function as a bacterial barrier. Typically the pore size is 0.2μm. Suitable materials for the filter material of the filter element 130include 0.2 micron Gore™ expanded PTFE from the MMT range, PALLVersapore™ 200R, and Donaldson™ TX6628. Larger pore sizes can also beused but these may require a secondary filter layer to ensure fullbioburden containment. As wound fluid contains lipids it is preferable,though not essential, to use an oleophobic filter membrane for example1.0 micron MMT-332 prior to 0.2 micron MMT-323. This prevents the lipidsfrom blocking the hydrophobic filter. The filter element can be attachedor sealed to the port and/or the cover film 140 over the orifice 145.For example, the filter element 130 may be molded into the port 150, ormay be adhered to both the top of the cover layer 140 and bottom of theport 150 using an adhesive such as, but not limited to, a UV curedadhesive.

It will be understood that other types of material could be used for thefilter element 130. More generally a microporous membrane can be usedwhich is a thin, flat sheet of polymeric material, this containsbillions of microscopic pores. Depending upon the membrane chosen thesepores can range in size from 0.01 to more than 10 micrometers.Microporous membranes are available in both hydrophilic (waterfiltering) and hydrophobic (water repellent) forms. In some embodimentsof the invention, filter element 130 comprises a support layer and anacrylic co-polymer membrane formed on the support layer. Preferably thewound dressing 100 according to certain embodiments of the presentinvention uses microporous hydrophobic membranes (MHMs). Numerouspolymers may be employed to form MHMs. For example, PTFE, polypropylene,PVDF and acrylic copolymer. All of these optional polymers can betreated in order to obtain specific surface characteristics that can beboth hydrophobic and oleophobic. As such these will repel liquids withlow surface tensions such as multi-vitamin infusions, lipids,surfactants, oils and organic solvents.

MHMs block liquids whilst allowing air to flow through the membranes.They are also highly efficient air filters eliminating potentiallyinfectious aerosols and particles. A single piece of MHM is well knownas an option to replace mechanical valves or vents. Incorporation ofMHMs can thus reduce product assembly costs improving profits andcosts/benefit ratio to a patient.

The filter element 130 may also include an odor absorbent material, forexample activated charcoal, carbon fiber cloth or Vitec Carbotec-RTQ2003073 foam, or the like. For example, an odor absorbent material mayform a layer of the filter element 130 or may be sandwiched betweenmicroporous hydrophobic membranes within the filter element.

The filter element 130 thus enables gas to be exhausted through theorifice 145. Liquid, particulates and pathogens however are contained inthe dressing.

In FIG. 1B, an embodiment of the wound dressing 100 is illustrated whichcomprises spacer elements 152, 153 in conjunction with the port 150 andthe filter 130. With the addition of such spacer elements 152, 153, theport 150 and filter 130 may be supported out of direct contact with theabsorbent layer 110 and/or the transmission layer 105. The absorbentlayer 110 may also act as an additional spacer element to keep thefilter 130 from contacting the transmission layer 105. Accordingly, withsuch a configuration contact of the filter 130 with the transmissionlayer 105 and wound fluids during use may thus be minimized. Ascontrasted with the embodiment illustrated in FIG. 1A, the aperture 146through the absorbent layer 110 may not necessarily need to be as largeor larger than the port 150, and would thus only need to be large enoughsuch that an air path can be maintained from the port to thetransmission layer 105 when the absorbent layer 110 is saturated withwound fluids.

In particular for embodiments with a single port 150 and through hole,it may be preferable for the port 150 and through hole to be located inan off-center position as illustrated in FIGS. 1A-B and in FIG. 2. Sucha location may permit the dressing 100 to be positioned onto a patientsuch that the port 150 is raised in relation to the remainder of thedressing 100. So positioned, the port 150 and the filter 130 may be lesslikely to come into contact with wound fluids that could prematurelyocclude the filter 130 so as to impair the transmission of negativepressure to the wound site.

FIG. 11 shows a plan view of a suction port 150 according to someembodiments of the invention. The suction port comprises a sealingsurface 152 for sealing the port to a wound dressing, a connectorportion 154 for connecting the suction port 150 to a source of negativepressure, and a hemispherical body portion 156 disposed between thesealing surface 152 and the connector portion 154. Sealing surface 152comprises a flange that provides a substantially flat area to provide agood seal when the port 150 is sealed to the cover layer 140. Connectorportion 154 is arranged to be coupled to the external source of negativepressure via a length of tube 220.

According to some embodiments, the filter element 130 forms part of thebacterial barrier over the wound site, and therefore it is importantthat a good seal is formed and maintained around the filter element.However, it has been determined that a seal formed by adhering thefilter element 130 to the cover layer 140 is not sufficiently reliable.This is a particular problem when a moisture vapor permeable cover layeris used, as the water vapor transpiring from the cover layer 140 canaffect the adhesive, leading to breach of the seal between the filterelement and the cover layer. Thus, according to some embodiments of theinvention an alternative arrangement for sealing the filter element 130to stop liquid from entering the connector portion 154 is employed.

FIG. 12 illustrates a cross section through the suction port 150 of FIG.11 according to some embodiments of the invention, the line A-A in FIG.11 indicating the location of the cross section. In the suction port ofFIG. 12, the suction port 150 further comprises filter element 130arranged within the body portion 156 of the suction port 150. A sealbetween the suction port 150 and the filter element 130 is achieved bymolding the filter element within the body portion of the suction port150.

FIG. 13 illustrates a cross section through the suction port 150 of FIG.11 according to some embodiments of the invention. In the suction portof FIG. 13, the filter element 130 is sealed to the sealing surface 152of the suction port 150. The filter element may be sealed to the sealingsurface using an adhesive or by welding the filter element to thesealing surface.

By providing the filter element 130 as part of the suction port 150, asillustrated in FIGS. 12 and 13, the problems associated with adheringthe filter element to the cover layer 140 are avoided allowing areliable seal to be provided. Furthermore, providing a sub-assemblyhaving the filter element 130 included as part of the suction port 150allows for simpler and more efficient manufacture of the wound dressing100.

While the suction port 150 has been described in the context of thewound dressing 100 of FIG. 1, it will be understood that the embodimentsof FIGS. 12 and 13 are applicable to any wound dressing for applying anegative pressure to a wound, wherein wound exudate drawn from the woundis retained within the dressing. According to some embodiments of theinvention, the suction port 150 may be manufactured from a transparentmaterial in order to allow a visual check to be made by a user for theingress of wound exudate into the suction port 150.

The wound dressing 100 and its methods of manufacture and use asdescribed herein may also incorporate features, configurations andmaterials described in the following patents and patent applicationsincorporated by reference in their entireties: U.S. Pat. Nos. 7,524,315,7,708,724, and 7,909,805; U.S. Patent Application Publication Nos.2005/0261642, 2007/0167926, 2009/0012483, 2009/0254054, 2010/0160879,2010/0160880, 2010/0174251, 2010/0274207, 2010/0298793, 2011/0009838,2011/0028918, 2011/0054421, and 2011/0054423; as well as U.S.application Ser. No. 12/941,390, filed Nov. 8, 2010, Ser. No.29/389,782, filed Apr. 15, 2011, and Ser. No. 29/389,783, filed Apr. 15,2011. From these incorporated by reference patents and patentapplications, features, configurations, materials and methods ofmanufacture or use for similar components to those described in thepresent disclosure may be substituted, added or implemented intoembodiments of the present application.

In operation the wound dressing 100 is sealed over a wound site forminga wound cavity. A pump unit (illustrated in FIG. 28 and described infurther detail below) applies a negative pressure at a connectionportion 154 of the port 150 which is communicated through the orifice145 to the transmission layer 105. Fluid is drawn towards the orificethrough the wound dressing from a wound site below the wound contactlayer 102. The fluid moves towards the orifice through the transmissionlayer 105. As the fluid is drawn through the transmission layer 105wound exudate is absorbed into the absorbent layer 110.

Turning to FIG. 2 which illustrates a wound dressing 100 in accordancewith an embodiment of the present invention one can see the uppersurface of the cover layer 140 which extends outwardly away from acentre of the dressing into a border region 200 surrounding a centralraised region 201 overlying the transmission layer 105 and the absorbentlayer 110. As indicated in FIG. 2 the general shape of the wounddressing is rectangular with rounded corner regions 202. It will beappreciated that wound dressings according to other embodiments of thepresent invention can be shaped differently such as square, circular orelliptical dressings, or the like.

The wound dressing 100 may be sized as necessary for the size and typeof wound it will be used in. In some embodiments, the wound dressing 100may measure between 20 and 40 cm on its long axis, and between 10 to 25cm on its short axis. For example, dressings may be provided in sizes of10×20 cm, 10×30 cm, 10×40 cm, 15×20 cm, and 15×30 cm. In someembodiments, the wound dressing 100 may be a square-shaped dressing withsides measuring between 15 and 25 cm (e.g., 15×15 cm, 20×20 cm and 25×25cm). The absorbent layer 110 may have a smaller area than the overalldressing, and in some embodiments may have a length and width that areboth about 3 to 10 cm shorter, more preferably about 5 cm shorter, thanthat of the overall dressing 100. In some rectangular-shape embodiments,the absorbent layer 110 may measure between 10 and 35 cm on its longaxis, and between 5 and 10 cm on its short axis. For example, absorbentlayers may be provided in sizes of 5.6×15 cm or 5×10 cm (for 10×20 cmdressings), 5.6×25 cm or 5×20 cm (for 10×30 cm dressings), 5.6×35 cm or5×30 cm (for 10×40 cm dressings), 10×15 cm (for 15×20 cm dressings), and10×25 cm (for 15×30 cm dressings). In some square-shape embodiments, theabsorbent layer 110 may have sides that are between 10 and 20 cm inlength (e.g., 10×10 cm for a 15×15 cm dressing, 15×15 cm for a 20×20 cmdressing, or 20×20 cm for a 25×25 cm dressing). The transmission layer105 is preferably smaller than the absorbent layer, and in someembodiments may have a length and width that are both about 0.5 to 2 cmshorter, more preferably about 1 cm shorter, than that of the absorbentlayer. In some rectangular-shape embodiments, the transmission layer maymeasure between 9 and 34 cm on its long axis and between 3 and 5 cm onits short axis. For example, transmission layers may be provided insizes of 4.6×14 cm or 4×9 cm (for 10×20 cm dressings), 4.6×24 cm or 4×19cm (for 10×30 cm dressings), 4.6×34 cm or 4×29 cm (for 10×40 cmdressings), 9×14 cm (for 15×20 cm dressings), and 9×24 cm (for 15×30 cmdressings). In some square-shape embodiments, the transmission layer mayhave sides that are between 9 and 19 cm in length (e.g., 9×9 cm for a15×15 cm dressing, 14×14 cm for a 20×20 cm dressing, or 19×19 cm for a25×25 cm dressing).

It will be understood that according to embodiments of the presentinvention the wound contact layer is optional. This layer is, if used,porous to water and faces an underlying wound site. A transmission layer105 such as an open celled foam, or a knitted or woven spacer fabric isused to distribute gas and fluid removal such that all areas of a woundare subjected to equal pressure. The cover layer together with thefilter layer forms a substantially liquid tight seal over the wound.Thus when a negative pressure is applied to the port 150 the negativepressure is communicated to the wound cavity below the cover layer. Thisnegative pressure is thus experienced at the target wound site. Fluidincluding air and wound exudate is drawn through the wound contact layerand transmission layer 105. The wound exudate drawn through the lowerlayers of the wound dressing is dissipated and absorbed into theabsorbent layer 110 where it is collected and stored. Air and moisturevapor is drawn upwards through the wound dressing through the filterlayer and out of the dressing through the suction port. A portion of thewater content of the wound exudate is drawn through the absorbent layerand into the cover layer 140 and then evaporates from the surface of thedressing.

As discussed above, when a negative pressure is applied to a wounddressing sealed over a wound site, fluids including wound exudate aredrawn from the wound site and through the transmission layer 105 towardsthe orifice 145. Wound exudate is then drawn into the absorbent layer110 where it is absorbed. However, some wound exudate may not beabsorbed and may move to the orifice 145. Filter element 130 provides abarrier that stops any liquid in the wound exudate from entering theconnection portion 154 of the suction port 150. Therefore, unabsorbedwound exudate may collect underneath the filter element 130. Ifsufficient wound exudate collects at the filter element, a layer ofliquid will form across the surface of filter element 130 and the filterelement will become blocked as the liquid cannot pass through the filterelement 130 and gases will be stopped from reaching the filter elementby the liquid layer. Once the filter element becomes blocked, negativepressure can no longer be communicated to the wound site, and the wounddressing must be changed for a fresh dressing, even though the totalcapacity of the absorbent layer has not been reached.

In a preferred embodiment, the port 150, along with any aperture 146 inthe absorbing layer 110 situated below it, generally aligns with themid-longitudinal axis A-A illustrated in FIG. 2. Preferably, the port150 and any such aperture 146 are situated closer to one end of thedressing, contrasted with a central position. In some embodiments, theport may be located at a corner of the dressing 100. For example, insome rectangular embodiments, the port 150 may be located between 4 and6 cm from the edge of the dressing, with the aperture 146 located 2 to 3cm from the edge of the absorbent layer. In some square embodiments, theport 150 may be located between 5 to 8 cm from the corner of thedressing, with the aperture 146 located 3 to 5 cm from the corner of theabsorbent layer.

Certain orientations of the wound dressing may increase the likelihoodof the filter element 130 becoming blocked in this way, as the movementof the wound exudate through the transmission layer may be aided by theeffect of gravity. Thus, if due to the orientation of the wound site andwound dressing, gravity acts to increase the rate at which wound exudateis drawn towards the orifice 145, the filter may become blocked withwound exudate more quickly. Thus, the wound dressing would have to bechanged more frequently and before the absorbent capacity of theabsorbent layer 110 has been reached.

In order to avoid the premature blocking of the wound dressing 100 bywound exudate drawn towards the orifice 145 some embodiments of theinvention include at least one element configured to reduce the rate atwhich wound exudate moves towards the orifice 145. The at least oneelement may increase the amount of exudate that is absorbed into theabsorbent layer before reaching the orifice 145 and/or may force thewound exudate to follow a longer path through the dressing beforereaching the orifice 145, thereby increasing the time before the wounddressing becomes blocked.

FIG. 3 shows a plan view of a wound dressing including baffle elementsthat reduce the rate at which wound exudate moves towards the orificeaccording to one embodiment of the invention. The wound dressingillustrated in FIG. 3 is similar to that shown in FIGS. 1 and 2, butincludes a number of baffle elements 310 disposed across the centralraised region 201. The baffle elements 310 form barriers in the centralregion of the dressing, which arrest the movement of wound exudatetowards the orifice.

Embodiments of baffle elements that may be used in the wound dressingdescribed herein are preferably at least partly flexible, so as topermit the wound dressing to flex and conform with the skin of thepatient surrounding the wound site. When so present in the wounddressing, the baffle elements are preferably constructed so as to atleast partially prevent liquid from flowing directly to the wounddressing port or orifice and its associated filter, if so provided. Thebaffle elements thus increase the distance that liquids may require toreach the port, which may help in absorbing these fluids into theabsorbent or superabsorbent material of the wound dressing.

According to some embodiments of the invention, the baffle element maycomprise a sealing region in which the absorbent layer 110 andtransmission layer 105 are absent and cover layer 140 is sealed to thewound contact layer 101. Thus, the baffle element presents a barrier tothe motion of the wound exudate, which must therefore follow a path thatavoids the baffle element. Thus the time taken for the wound exudate toreach the orifice is increased.

In some embodiments, the baffle elements may be an insert of asubstantially non-porous material, for example a closed-cellpolyethylene foam, placed inside the dressing. In some cases, it may bepreferable to place such an inserted baffle element in a sealing regionwhere one or more of the absorbent layer 110 and/or transmission layer105 are absent. A sealant, for example a viscous curing sealant such asa silicone sealant, could be placed or injected as a thin strip so as toform a baffle element that is substantially liquid impermeable. Such abaffle element could be placed or injected into a region of thetransmission layer 105 and/or absorbent layer 110, or also a sealingregion where the absorbent layer 110 and/or transmission layer 105 areabsent.

FIG. 6 illustrates a wound dressing including a baffle element accordingto a further embodiment of the invention. A single baffle element 610provides a cup shaped barrier between the bulk of the absorbent layer110 and the orifice 145. Thus wound exudate that is initially drawn fromthe wound site within the region defined by the baffle element 610, mustfollow a path around the outside of the cup shaped barrier to reach theorifice 145. As will be recognized, the baffle element 610 reduces theeffect of gravity on reducing the time taken for the wound exudate tomove to the orifice 145, as for most orientations of the wound dressingat least a part of the path taken by the wound exudate will be againstthe force of gravity.

The embodiments of FIGS. 3 and 6 have been described with respect to awound dressing having a structure as shown in FIG. 1. However, it willbe understood that the baffle elements could equally be applied to awound dressing in which the transmission layer 105 was absent.

FIG. 4 shows a plan view of a wound dressing including the at least oneelement according to one embodiment of the invention in which a numberof baffle elements 410 are provided that extend across the width of thecentral region 201 of the wound dressing, with further baffle elements412 formed in a semi-circular path around the orifice 145.

FIG. 5 illustrates the configuration of baffle elements 410 according tosome embodiments of the invention. The baffle element comprises achannel of absorbent material 510 underlying the transmission layer 105.A channel in the absorbent layer 110 is located over the baffle element410 so that the transmission layer is in contact with the cover layer140 in the region of the baffle element 410. Thus, wound exudate that ismoving along a lower surface of the transmission layer 105, and hastherefore not been drawn into absorbent layer 110, will come intocontact with and be absorbed by the channel of absorbent material 510.

Alternatively, or additionally, baffle elements may comprise one or morechannels provided in the surface of the transmission layer 105underlying and abutting the absorbent layer 110. In use, when negativepressure is applied to the wound dressing, the absorbent layer 110 willbe drawn into the channel. The channel in the transmission layer mayhave a depth substantially equal to the depth of the transmission layer,or may have a depth less than the depth of the transmission layer. Thedimensions of the channel may be chosen to ensure that the channel isfilled by the absorbent layer 110 when negative pressure is applied tothe wound dressing. According to some embodiments, the channel in thetransmission layer comprises a channel of absorbent material in thetransmission layer 105.

The baffle elements may be formed into a range of shapes and patterns,for example FIGS. 14A to 14L illustrate wound dressings having a numberof different exemplifying configurations of baffle elements. FIG. 14Aillustrates a linear baffle element in a vertical configuration alignedin the direction of the port or orifice. FIG. 14B illustrates anX-shaped baffle element. FIGS. 14C-E illustrate embodiments of wounddressings with multiple baffle elements, aligned in a generallydiagonal, horizontal, or vertical manner.

FIG. 14F illustrates baffle elements arranged in a six-armed starburstconfiguration, with a center portion left open. FIG. 14G illustrates aW-shaped baffle element on the wound dressing in a position distal tothe port or orifice. In FIG. 14H, an 3-by-3 array of X-shaped baffleelements is provided on the wound dressing, although it will beunderstood that more or less X-shaped baffle elements may be used. FIG.14I shows an embodiment with a plurality of rectangular baffle elements,and wherein one or more baffle elements are located underneath the portin the wound dressing. FIGS. 14J-K illustrate wound dressing embodimentswith longer diagonal and horizontal baffle elements. In FIG. 14L,rectangular baffle elements are present on this embodiment of a wounddressing, wherein the baffle elements are of different sizes.

According to some embodiments of the invention, the at least one elementcomprises an array of vias, or troughs, in the transmission layer 105.FIG. 15 illustrates a transmission layer 105 that is perforated withdiamond shaped vias 210. The vias 210 are arranged such that no linearpathway exists through the pattern of vias that does not intersect withone or more of the vias 210.

When negative pressure is applied to the wound dressing, the absorbentlayer 110 is drawn into the vias 210, increasing the area of theabsorbent layer that comes into contact with wound exudate being drawnthrough the transmission layer 105. Alternatively, the vias 210 may befilled with further absorbent material for absorbing wound exudate beingdrawn through the transmission layer 105. The vias may extend throughthe depth of the transmission layer 105, or may extend through only partof the transmission layer.

Wound exudate moving through the transmission layer 105 under theinfluence of gravity will fall through the transmission layer in asubstantially linear manner. Any such linear pathways will, at somepoint, intersect with one of the vias 210, and thus the exudate will bebrought into contact with absorbent material within the vias 210. Woundexudate coming into contact with absorbent material will be absorbed,stopping the flow of the wound exudate through the transmission layer105, and reducing the amount of unabsorbed wound exudate that mayotherwise pool around the orifice. It will be appreciated that the viasare not limited to diamond shapes, and that any pattern of vias may beused. Preferably, the vias will be arranged to ensure that all linearpaths through the transmission layer 105 intersect with at least onevia. The pattern of vias may be chosen to minimize the distance thatwound exudate is able to travel though the transmission layer beforeencountering a via and being absorbed.

FIG. 7 illustrates a wound dressing in accordance with some embodimentsof the invention in which the at least one element comprises an airchannel 710 connecting the central region 201 of the wound dressing tothe orifice 145. In the embodiment of FIG. 7, the air channel 710extends from an edge region of the transmission layer 105 and connectsthe transmission layer to the orifice 145.

In use, wound exudate is drawn towards the orifice 145 by theapplication of negative pressure at the suction port 150. However, theair channel 710 present a relatively long serpentine path to be followedby the wound exudate before it reaches the orifice 145. This long pathincreases the time that negative pressure can be applied to the dressingbefore wound exudate traverses the distance between the transmissionlayer and the orifice and blocks the filter element 130, therebyincreasing the time the dressing can be in use before it must bereplaced.

FIG. 8 illustrates a wound dressing in accordance with one embodiment ofthe invention in which the at least one element comprises air channels810 and 812 connecting the central region 201 of the wound dressing tothe orifice 145. Channels 810 and 812 are coupled to the transmissionlayer at substantially opposite corners of the central region 201.

The wound dressing shown in FIG. 8 reduces the effect of gravity on thetime taken for the orifice to become blocked. If the wound dressing isin an orientation in which wound exudate moves under the influence ofgravity towards the edge region of the transmission layer connected toair channel 810, the effect of gravity will be to move wound exudateaway from the edge region of the transmission layer coupled to airchannel 812, and vice versa. Thus, the embodiment of FIG. 8 providesalternative air channels for coupling the negative pressure to thetransmission layer such that, should one air channel become blocked aremaining air channel should remain open and able to communicate thenegative pressure to the transmission layer 105, thereby increasing thetime before negative pressure can no longer be applied to the wounddressing and the dressing must be changed.

Further embodiments of the invention may comprise greater numbers of airchannels connecting the transmission layer 105 to the orifice.

According to some embodiments of the invention, two or more orifices maybe provided in the cover layer 140 for applying the negative pressure tothe wound dressing. The two or more orifices can be distributed acrossthe cover layer 140 such that if one orifice becomes blocked by woundexudate due to the wound dressing being in a particular orientation, atleast one remaining orifice would be expected to remain unblocked. Eachorifice is in fluid communication with a wound chamber defined by thewound dressing, and is therefore able to communicate the negativepressure to the wound site.

FIG. 9 illustrates a wound dressing in accordance with a furtherembodiment of the invention. The wound dressing of FIG. 9 is similar tothat of FIGS. 1A-B but includes two orifices 145 and 845 provided in thecover layer 140. A fluid communication passage connects the two orificessuch that a negative pressure applied to one of the orifices iscommunicated to the remaining orifice via the fluid communicationpassage. The orifices 145, 845 are located in opposite corner regions ofthe cover layer 140. The fluid communication passage is formed using aflexible molding 910 on the upper surface of the cover layer 140. Itwill be appreciated that the flexible molding may be formed from othersuitable means for example a strip of transmission or open porous foamlayer placed on the cover layer 140 between the orifices 145 and 845 anda further film welded or adhered over the strip thus sealing it to thecover layer and forming a passageway through the foam. A conduit maythen be attached in a known manner to the sealing film for applicationof negative pressure.

In use, the wound dressing having two orifices is sealed over a woundsite to form a wound cavity and an external source of negative pressureis applied to one of the orifices 145, 845, and the negative pressurewill be communicated to the remaining orifice via the fluidcommunication passage. Thus, the negative pressure is communicated viathe two orifices 145, 845 to the transmission layer 105, and thereby tothe wound site. If one of the orifices 145, 845 becomes blocked due towound exudate collecting at the orifice under the influence of gravity,the remaining orifice should remain clear, allowing negative pressure tocontinue to be communicated to the wound site. According to someembodiments, the transmission layer 105 may be omitted, and the twoorifices will communicate the negative pressure to the wound site viathe absorbent layer 110.

FIG. 10 illustrates a side view of the fluid communication passage ofthe embodiment of FIG. 9. Molding 910 is sealed to the top surface ofthe cover layer 140, and covering orifices 145 and 845. Gas permeableliquid impermeable filter elements 130 are provided at each orifice. Themolding 910 is coupled to an external source of negative pressure via atube element 220.

According to some embodiments, a single filter element may be usedextending underneath the length of the fluid communication passage andthe two orifices. While the above example embodiment has been describedas having two orifices, it will be understood that more than twoorifices could be used, the fluid communication passage allowing thenegative pressure to be communicated between the orifices.

FIG. 16 illustrates an alternative arrangement in which a singleelongate orifice 350 is provided in the cover layer 140. First andsecond ends 355, 356 of the orifice 350 are located in opposite cornerregions of the cover layer 140. A flexible molding 360 is sealed aroundthe orifice 350 and allows negative pressure to be communicated throughthe cover layer 140 along the length of the orifice 350. The flexiblemolding 360 may be formed by any suitable means as described above inrelation to flexible molding 910.

In use, the wound dressing is sealed over a wound site to form a woundcavity and an external source of negative pressure is applied to theorifice. If, due to the orientation of the wound dressing, wound exudatemoves under the influence of gravity to collect around one end 355 ofthe orifice 350, a portion of the orifice 350 near to the end 355 willbecome blocked. However, a portion of the orifice near to the remainingend 356 should remain clear, allowing continued application of negativepressure to the wound site.

As still further options the dressing can contain anti-microbial e.g.nanocrystalline silver agents on the wound contact layer and/or silversulphur diazine in the absorbent layer. These may be used separately ortogether. These respectively kill micro-organisms in the wound andmicro-organisms in the absorption matrix. As a still further optionother active components, for example, pain suppressants, such asibuprofen, may be included. Also agents which enhance cell activity,such as growth factors or that inhibit enzymes, such as matrixmetalloproteinase inhibitors, such as tissue inhibitors ofmetalloproteinase (TIMPS) or zinc chelators could be utilized. As astill further option odor trapping elements such as activated carbon,cyclodextrine, zeolite or the like may be included in the absorbentlayer or as a still further layer above the filter layer.

FIG. 17 illustrates a first, upper surface 1700 and a further, lowersurface 1702 of a transmission layer 105 according to an embodiment ofthe present invention. In the embodiment illustrated in FIG. 17 fibers1703 of a woven layer extend between the first surface 1700 and thefurther surface 1702. It will be appreciated that according to furtherembodiments of the present invention if a foam layer is used as atransmission layer 105 the connected strands forming the foam will actas spacer elements. As illustrated in FIG. 17 in a relaxed mode ofoperation, that is to say when in use, no negative pressure is appliedto the wound dressing or negative pressure is applied to the wounddressing but no external force acts on the wound dressing then thefibers 1703 extend substantially perpendicular to the upper and lowersurfaces keeping the surfaces in a spaced apart substantially parallelconfiguration.

FIG. 18 illustrates the transmission layer 105 when an external force isexerted on the outside of the dressing. The external force can be acompressive force indicated by arrow A and/or a lateral forceillustrated by arrow B in FIG. 18. As indicated either a compressiveforce or a lateral force acts to cause the fibers 1703 to lean to oneside. This causes the upper and lower surfaces to become laterallyoffset with respect to each other as well as causing the thickness ofthe layer to reduce from a separation distance r indicated in FIG. 17 ina relaxed mode of operation to a compression distance c illustrated inFIG. 18. The reduction in thickness effectively provides some “give” inthe dressing even when the dressing is subject to negative pressure. Itwill be appreciated that the forces acting on the dressing may occurthroughout the whole of the surface area of the dressing or only in oneor more particular regions. In such a situation regions of the dressingcan be in a relaxed mode of operation and further regions can be in acompressed mode of operation. As illustrated in FIG. 18 when a force isexerted on the transmission layer the fibers separating the upper andlower surfaces tend to lean to one side sharing a common lean angle.

Throughout this specification reference will be made to a relaxed modeof operation and a forced mode of operation. It is to be understood thatthe relaxed mode of operation corresponds to a natural state of thematerial either when no negative pressure is applied or when negativepressure is applied. In either situation no external force, caused forexample by motion of a patient or an impact is in evidence. By contrasta forced mode of operation occurs when an external force whethercompressive, lateral or other is brought to bear upon the wounddressing. Such forces can cause serious damage/prevent healing or awound.

FIG. 19 illustrates how certain embodiments of the present invention canalso operate to offset load forces. As illustrated in FIG. 19 if a forceis exerted over a contact area 1900 in an upper surface 1700 of thetransmission layer 105 then this force is transmitted across and throughthe transmission layer and is exerted over a larger dissipation area1901 against an underlying wound site. In the case of use of a 3D knitas a transmission layer this is because the relatively stiff spacerelements provide at least some lateral stiffness to the layer.

FIG. 20 illustrates the transmission layer 105 and absorbent layer 110of some embodiments in more detail. The absorbent layer 110 is locatedproximate to the upper surface 1700 of the transmission layer 105 and isunbonded thereto according to certain embodiments of the presentinvention. When unbonded the absorbent layer 110 is also able to movelaterally with respect to the underlying transmission layer when alateral or shear force is applied to the wound dressing. Also theabsorbent layer is able to further compress when a compressive forceillustrated in FIG. 21 acts on the wound dressing. As illustrated inFIG. 21 the absorbent layer 110 decreases in thickness under acompressive force from a non-compressed thickness x illustrated in FIG.20 to a compressed distance y illustrated in FIG. 21. The compressiveforce also acts to offset the upper and lower surfaces of thetransmission layer as described above thus enhancing the “give” of thedressing. The ability for an upper surface 2201 to translate laterallywith respect to a lower surface 2202 of the absorbent layer under alateral or shearing force exerted on the wound dressing is illustratedin more detail in FIG. 22. This lateral motion causes the thickness x ofthe absorbent layer 110 to reduce and the upper surface and lowersurface of the absorbent layer to be offset with respect to each other.This effect can itself be sufficient to prevent shear forces exerted onthe whole or part of the wound dressing from being transferred to anunderlying wound bed. As can the corresponding effect in thetransmission layer. However a combination enhances the cushioningeffect. If the wound bed comprises a skin graft region the reduction ofshear forces can be particularly advantageous.

It is to be noted that in use the dressing may be used “up-side down”,at an angle or vertical. References to upper and lower are thus used forexplanation purposes only.

FIG. 23 illustrates a cross-section of a portion of an embodiment of adressing shown in FIGS. 1A-2. In particular, FIG. 23 illustrates amagnified view of the wound contact layer 102 which includes a lowersurface 101 and multiple perforations 104 formed as through holes. Anupper surface 104 of the wound contact layer abuts a first layer 300 ofthe transmission layer 105. A further, upper, layer 301 of thetransmission layer 105 is spaced apart from the first layer. The firstand further layers of the transmission layer are kept apart in a spacedapart relationship by multiple mono-filament fiber spacers 302 which actas resilient flexible pillars separating the two layers of thetransmission layer. The upper layer 301 of the transmission layer isadjacent a lower surface of the absorbent 110 which, for example, isformed as a pad of fibrous cellulose material interspaced withsuper-absorbent particulate matter.

FIG. 24 illustrates the lower layer of the 3D fabric transmission layerin more detail. The 3D fabric layer 105 is formed as a lower and upperknitted layer given a loft by the knitted structure. Rows of the knittedstitches may be referred to as a course of stitches. Columns of stitchesmay be referred to as a whale. A single monofilament fiber is knittedinto the 3D fabric to form the multiple separating strands.

As illustrated in FIG. 24 there are apertures or openings formed betweeninterlocked stitches in the lower layer of the transmission layer 105.In use, wound exudate including liquid and semi-solid e.g. viscousslurry, suspensions of biological debris or the like and solid materialwill pass upwards through the perforations 104 in the wound contactlayer and through the openings in the inter knitted structure of thefirst layer 300 of the transmission layer. The openings between theinterconnected stitches have an average open area ranging from around250 microns to 450 microns. The particular open area in the first layerof the transmission layer will be determined by the materials and methodof manufacture of the lower layer. FIG. 25 illustrates how an open areaof openings in the further layer above the first layer (that is to sayfurther away from the wound) can include openings which have a greateropen area than the openings in the lower layer. In this way as woundexudate which includes semi-solid and solid matter moves from the woundbed at the wound site upwards into the wound dressing any particulatematter which is of a size small enough to pass through the relativesmall openings 400 in the lower layer will certainly be able to passthrough the larger area openings 501 in the upper area. This helps avoiddebris in the form of solid material collecting in the interstitialregion between the monofilament fibers between the upper and lowerlayer. As shown in FIG. 25, the upper layer 301 may include openings 500similar to the openings 400 in the lower layer 300. However, during theknitting process the upper surface is knitted so that larger open areaopenings 501 are interspersed across the whole surface of the upperlayer. As illustrated in FIG. 25 the larger open area openings 501 canhave an open range considerably larger (shown between 700 to 800microns). The lower layer 300 thus acts to some extent as a filteringlayer having openings 400 which enable gas and liquid to pass freelytherethrough but to prevent solid and semi-solid particulate matterwhich is too large from passing in to the interstitial region in thetransmission layer 105. This helps keep a flowpath along thetransmission layer open.

By providing openings in an upper layer in the transmission layer whichhave a greater open area than any openings in the lower area build-up ofsolid particulate matter in the interstitial region between the upperand lower layers of the transmission layer is avoided since any solid orsemi-solid matter will flow along the channel and eventually be enabledto pass upwards through the larger openings where the material is takenup by the super-absorber/absorbent material.

The absorbent layer 110 holds liquid collected during the application ofnegative pressure therapy. By having this layer in fluid communicationwith, and preferably in contact with, the layer of the transmissionlayer, the region of the transmission layer 105 is kept at a moistenvironment. This helps avoid build-up and crusting of the exudateduring use.

FIG. 26 illustrates an alternative material which could be utilized asthe transmission layer in a wound dressing. In particular, FIG. 26illustrates a lower surface of a 3D knit material which may be utilizedas the transmission layer. Openings 600 are formed in the surface whichenables wound exudate and air to pass from the wound through a woundcontact layer which would be located on the surface shown in FIG. 6 andthrough those openings. FIG. 27 illustrates an upper surface of thematerial shown in FIG. 26 and illustrates how larger openings 700 may beformed in the upper surface.

Whilst certain embodiments of the present invention have so far beendescribed in which the transmission layer is formed as a 3D knit layer,e.g., two layers spaced apart by a monofilament layer, it will beappreciated that certain embodiments of the present invention are notrestricted to the use of such a material. In some embodiments, as analternative to such a 3D knit material one or more layers of a widevariety of materials could be utilized. In each case, according toembodiments of the present invention, the openings presented by layersof the transmission layer are wider and wider as one moves away from theside of the dressing which, in use will be located proximate to thewound. In some embodiments, the transmission layer may be provided bymultiple layers of open celled foam. In some embodiments, the foam isreticulated open cell foam. Preferably, the foam is hydrophilic or ableto wick aqueous based fluids. The pore size in each layer is selected sothat in the foam layer most proximate to the wound side in use the poreshave a smallest size. If only one further foam layer is utilized thatincludes pore sizes which are greater than the pore sizes of the firstlayer. This helps avoid solid particulate being trapped in the lowerlayer which thus helps maintain the lower layer in an open configurationin which it is thus able to transmit air throughout the dressing. Incertain embodiments, two, three, four or more foam layers may beincluded. The foam layers may be integrally formed, for example, byselecting a foam having a large pore size and then repeatedly dippingthis to a lesser and lesser extent into material which will clog thepores or alternatively, the transmission layer formed by the multiplefoam layers may be provided by laminating different types of foam in alayered arrangement or by securing such layers of foam in place in aknown manner.

According to certain embodiments of the present invention, thetransmission layer is formed by multiple layers of mesh instead of foamor 3D knit materials. For example, fine gauze mesh may be utilized for awound facing side of the transmission layer and a Hessian mesh having alarger pore size may be located on a distal side of the gauze meshfacing away from the wound in use. The one, two, three or more layers ofmesh can be secured together in an appropriate manner, such as beingstitched or adhered together or the like. The resultant mat of fibersprovides a transmittal layer through which air can be transmitted in thedressing but by selecting the opening sizes in the meshes as one movesthrough the dressing away from the wound contact side, the accumulationof solid particulate matter in lower layers can be avoided.

FIG. 28 illustrates an embodiment of a TNP wound treatment comprising awound dressing 100 in combination with a pump 800. Here, the dressing100 may be placed over a wound as described previously, and a conduit220 may then be connected to the port 150, although in some embodimentsthe dressing 100 may be provided with at least a portion of the conduit220 preattached to the port 150. Preferably, the dressing 100 isprovided as a single article with all wound dressing elements (includingthe port 150) pre-attached and integrated into a single unit. The wounddressing 100 may then be connected, via the conduit 220, to a source ofnegative pressure such as the pump 800. Preferably, the pump 800 isminiaturized and portable, although larger conventional pumps may alsobe used with the dressing 100. In some embodiments, the pump 800 may beattached or mounted onto or adjacent the dressing 100. A connector 221may also be provided so as to permit the conduit 220 leading to thewound dressing 100 to be disconnected from the pump, which may be usefulfor example during dressing changes.

FIGS. 29A-D illustrate the use of an embodiment of a TNP wound treatmentsystem being used to treat a wound site on a patient. FIG. 29A shows awound site 190 being cleaned and prepared for treatment. Here, thehealthy skin surrounding the wound site 190 is preferably cleaned andexcess hair removed or shaved. The wound site 190 may also be irrigatedwith sterile saline solution if necessary. Optionally, a skin protectantmay be applied to the skin surrounding the wound site 190. If necessary,a wound packing material, such as foam or gauze, may be placed in thewound site 190. This may be preferable if the wound site 190 is a deeperwound.

After the skin surrounding the wound site 190 is dry, and with referencenow to FIG. 29B, the wound dressing 100 may be positioned and placedover the wound site 190. Preferably, the wound dressing 100 is placedwith the wound contact layer 102 over and/or in contact with the woundsite 190. In some embodiments, an adhesive layer is provided on thelower surface 101 of the wound contact layer 102, which may in somecases be protected by an optional release layer to be removed prior toplacement of the wound dressing 100 over the wound site 190. Preferably,the dressing 100 is positioned such that the port 150 is in a raisedposition with respect to the remainder of the dressing 100 so as toavoid fluid pooling around the port. In some embodiments, the dressing100 is positioned so that the port 150 is not directly overlying thewound, and is level with or at a higher point than the wound. To helpensure adequate sealing for TNP, the edges of the dressing 100 arepreferably smoothed over to avoid creases or folds.

With reference now to FIG. 29C, the dressing 100 is connected to thepump 800. The pump 800 is configured to apply negative pressure to thewound site via the dressing 100, and typically through a conduit. Insome embodiments, and as described above in FIG. 28, a connector may beused to join the conduit from the dressing 100 to the pump 800. Upon theapplication of negative pressure with the pump 800, the dressing 100 mayin some embodiments partially collapse and present a wrinkled appearanceas a result of the evacuation of some or all of the air underneath thedressing 100. In some embodiments, the pump 800 may be configured todetect if any leaks are present in the dressing 100, such as at theinterface between the dressing 100 and the skin surrounding the woundsite 190. Should a leak be found, such leak is preferably remedied priorto continuing treatment.

Turning to FIG. 29D, additional fixation strips 195 may also be attachedaround the edges of the dressing 100. Such fixation strips 195 may beadvantageous in some situations so as to provide additional sealingagainst the skin of the patient surrounding the wound site 190. Forexample, the fixation strips 195 may provide additional sealing for whena patient is more mobile. In some cases, the fixation strips 195 may beused prior to activation of the pump 800, particularly if the dressing100 is placed over a difficult to reach or contoured area.

Treatment of the wound site 190 preferably continues until the wound hasreached a desired level of healing. In some embodiments, it may bedesirable to replace the dressing 100 after a certain time period haselapsed, or if the dressing is full of wound fluids. During suchchanges, the pump 800 may be kept, with just the dressing 100 beingchanged.

Throughout the description and claims of this specification, the words“comprise” and “contain” and variations of the words, for example“comprising” and “comprises”, mean “including but not limited to”, andis they are not intended to (and does not) exclude other moieties,additives, components, integers or steps.

Throughout the description and claims of this specification, thesingular encompasses the plural unless the context otherwise requires.In particular, where the indefinite article is used, the specificationis to be understood as contemplating plurality as well as singularity,unless the context requires otherwise.

Features, integers, characteristics, compounds, chemical moieties orgroups described in conjunction with a particular aspect, embodiment orexample of the invention are to be understood to be applicable to anyother aspect, embodiment or example described herein unless incompatibletherewith. All of the features disclosed in this specification(including any accompanying claims, abstract and drawings), and/or allof the steps of any method or process so disclosed, may be combined inany combination, except combinations where at least some of suchfeatures and/or steps are mutually exclusive. The invention is notrestricted to the details of any foregoing embodiments. The inventionextends to any novel one, or any novel combination, of the featuresdisclosed in this specification (including any accompanying claims,abstract and drawings), or to any novel one, or any novel combination,of the steps of any method or process so disclosed.

1-134. (canceled)
 135. A wound treatment apparatus comprising: a wounddressing comprising: a gas impermeable cover layer comprising anorifice; an absorbent layer for absorbing wound exudate, wherein theabsorbent layer comprises superabsorbent material; a transmission layer;a lower pressure sensitive adhesive layer to adhere the wound dressingto skin around the wound site; and a suction port sealed to the top ofthe cover layer over the orifice and configured to communicate negativepressure through the orifice; wherein the suction port is manufacturedfrom a transparent material and wherein the wound dressing and thesuction port are configured such that wound exudate collected by thewound dressing and located below the suction port is visible from abovethe suction port.
 136. The wound treatment of claim 135, wherein thesuction port is situated closer to one end of the dressing, contrastedwith a central position of the dressing.
 137. The wound treatmentapparatus of claim 135, further comprising a spacer element positionedover the gas impermeable cover layer configured to support the suctionport out of direct contact with the absorbent layer and/or thetransmission layer.
 138. The wound treatment apparatus of claim 135,further comprising a filter element attached to the suction port overthe orifice of the cover layer.
 139. The wound treatment apparatus ofclaim 138, wherein the filter element is adhered to both the top of thecover layer and to the bottom of the suction port using an adhesive.140. The wound treatment apparatus of claim 138, wherein the filterelement forms part of a bacterial barrier over the wound site.
 141. Thewound treatment apparatus of claim 135, wherein an upper surface of thecover layer extends outwardly away from a center of the dressing into aborder region surrounding a central raised region overlying thetransmission layer and the absorbent layer.
 142. The wound treatmentapparatus of claim 135, wherein the wound dressing includes at least oneelement configured to reduce the rate at which would exudate movestowards the orifice.
 143. The wound treatment apparatus of claim 142,wherein the at least one element is configured to increase the amount ofexudate absorbed into the absorbent layer before reaching the orificeand/or wherein the at least one element is configured to force the woundexudate to follow a longer path through the wound dressing.
 144. Thewound treatment apparatus of claim 135, wherein the suction portcomprises a sealing surface that provides a substantially flat areaconfigured to be sealed to the cover layer.
 145. The wound treatmentapparatus of claim 135, wherein the cover layer is configured to protectthe wound from external bacterial contamination and allow liquid fromwound exudate to be transferred through the layer and evaporated from anouter surface of the cover layer.
 146. The wound treatment apparatus ofclaim 135, wherein the cover layer is moisture vapor permeable.
 147. Thewound treatment apparatus of claim 135, wherein the wound dressingfurther comprises a wound contact layer.
 148. The wound treatmentapparatus of claim 147, wherein the wound contact layer is configured tohold the wound dressing together and act as a carrier for the lowerpressure sensitive adhesive layer.
 149. The wound treatment apparatus ofclaim 135, wherein the absorbent layer comprises one or more throughholes to provide a fluid flow pathway.
 150. The wound treatmentapparatus of claim 135, wherein the superabsorbent material comprises agel-forming material.
 151. The wound treatment apparatus of claim 135,wherein the suction port is generally aligned with a mid-longitudinalaxis of the wound dressing when viewed from above.
 152. The woundtreatment apparatus of claim 135, wherein the transmission layercomprises an open celled foam.
 153. The wound treatment apparatus ofclaim 135, further comprising a source of negative pressure configuredto be fluidly connected with the suction port.
 154. A wound treatmentapparatus comprising: a wound dressing comprising: a gas impermeablecover layer comprising an orifice; an absorbent layer for absorbingwound exudate, wherein the absorbent layer comprises superabsorbentmaterial; a lower pressure sensitive adhesive layer to adhere the wounddressing to skin around the wound site; and a suction port sealed to thetop of the cover layer over the orifice and configured to communicatenegative pressure through the orifice; wherein the suction port ismanufactured from a transparent material and wherein the wound dressingand the suction port are configured such that wound exudate collected bythe wound dressing and located below the suction port is visible fromabove the suction port; and wherein the suction port is situated closerto one end of the dressing, contrasted with a central position of thedressing.
 155. The wound treatment apparatus of claim 154, furthercomprising a spacer element positioned over the gas impermeable coverlayer configured to support the suction port out of direct contact withthe absorbent layer.
 156. The wound treatment apparatus of claim 154,further comprising a filter element attached to the suction port overthe orifice of the cover layer.
 157. The wound treatment apparatus ofclaim 156, wherein the filter element is adhered to both the top of thecover layer and to the bottom of the suction port using an adhesive.158. The wound treatment apparatus of claim 154, wherein the suctionport comprises a sealing surface that provides a substantially flat areaconfigured to be sealed to the cover layer.
 159. The wound treatmentapparatus of claim 154, wherein the superabsorbent material comprises agel-forming material.
 160. The wound treatment apparatus of claim 154,further comprising a source of negative pressure configured to befluidly connected with the suction port.